Cell Relay Archive

["Mad Kevo" <mad_kevo_obvious@hotmail.com>]

Maybe the term "head-of-queue blocking" is clearer... at least to us non
US-English speakers. ;-)
/Kev.


Hal Murray <murray@pa.dec.com> wrote in message
86jksk$pse@src-news.pa.dec.com">news:86jksk$pse@src-news.pa.dec.com...
>
> > Can anyone tell me what's the meaning of head-of-line blocking?
>
> Suppose you are building a switch or router and you decide
> to store packets in a FIFO rather than in RAM.
>
> Suppose each link has a separate FIFO and the packet on the
> front of the FIFO for link A wants to go out link B
> and the next one wants to go out link C.
>
> But suppose Link B is busy with another packet, say from link C.
>
> If link C (outgoing side) is idle, then you could send the
> second packet in the FIFO.  But you can't do that because
> it's a FIFO and you can only access the first packet.
>
> That's head of line blocking - packets behind the first
> one get blocked if the first one needs a resource that is busy.
>
> --
> These are my opinions, not necessarily my employers.